1. Field of the Invention
The present invention relates to an object recognition method for a mobile robot navigation, and more particularly, to a recognition method for recognizing quickly and reliably a land mark.
2. Description of the Related Art
Mobile robots are occasionally used to transport objects in plants. Guide lines are typically embedded in the ground or the floor inside the building of a plant, and a robot guides itself to its destination following the guide line. In this way, the robot moves to its destination with no operator intervention required.
In this case, however, the robot is allowed to follow a fixed robot path only, and if any unexpected obstacle lies in the path, the robot is unable to reach its destination.
To cope with such a situation, methods have been proposed which allow the robot to temporarily deviate from the guide line to evade an obstacle and then return back on the right track, when the obstacle lies in the middle of the track.
In this conventional method, since the robot follows the guide line, in principle, the construction of the guide line is essential. In the event of a layout modification of facilities in a plant, the guide line also needs modifying to match the new layout. Such a modification presents a great deal of difficulty in most cases.
Methods have also been proposed to allow a robot to receive a radio wave, for example, transmitted from a destination, and guide it in the direction in which the radio wave is coming. Since such a system needs to determine an absolute position within the workspace of the robot, the area in which the robot is able to move is limited and the entire system for robot navigation becomes a large and costly one.
It is then contemplated that, with a land mark (a sign) arranged, a robot is designed to autonomously travel referring to the land mark. With this arrangement, the robot may recognize the land mark using a television camera, for example, and allowed to move along a free robot path in a relatively simple fashion.
To autonomously move referring to the land mark, the robot needs to recognize the land mark. The land marks are conventionally formed to a predetermined standard shape to help the robot to easily recognize them. The output from a television camera is processed to determine whether each land mark matches the predetermined standard shape.
If associative memory is used to learn pixel images to determine whether a shape picked up matches a predetermined shape, the problem of a memory capacity limitation arises. Furthermore, similarly shaped land marks may be confusing to the robot.